People deciding between low-carb and low-fat diets should know that the research shows a slight advantage for low-carb diets when it comes to weight loss, according to an article published in December in The Journal of the American Osteopathic Association.
Physicians from the Mayo Clinic in Arizona found that low-carb diets, including Atkins, South Beach and Paleo, were safe for up to six months. Depending on the diet, participants lost 2.5 to almost 9 lb. more than those who followed a low-fat diet.
"The best conclusion to draw is that adhering to a short-term, low-carb diet appears to be safe and may be associated with weight reduction," said Dr. Heather Fields, an internal medicine physician at Mayo Clinic in Arizona and lead researcher on this study. "However, that weight loss is small and of questionable clinical significance in comparison to low-fat diets."
Analyzing research from January 2005 to April 2016, Fields reviewed articles that addressed potential adverse effects and the overall safety of low-carb diets. Diets that heavily restrict carbohydrates often lead to greater consumption of meats.
While available studies did not consistently address the source or quality of proteins and fats consumed in low-carb diets, they did show short-term efficacy in weight loss without negative effects on blood pressure, glucose and cholesterol compared with other diets.
However, Fields said the findings come with a caveat.
"Physicians must keep in mind that the literature is surprisingly limited, considering the popularity of these diets and the claims of health benefits in the public press," she said. "Our review found no safety issues identified in the current literature, but patients considering (low-carb diets) should be advised there is very little data on long-term safety and efficacy."
Fields also noted that limitations in the previous research she reviewed made it difficult to draw broad conclusions. For example, studies did not address the type of weight lost — whether muscle, water or fat — and studies primarily relied on participants' dietary recall, which is highly susceptible to error.
Fields' review found even the definition of a low-carb diet to be highly variable. While all were based on carbohydrate restriction, diets allowed carbs to account for anywhere between 4% and 46% of daily calories, which convolutes the evidence.
"As an osteopathic physician, I tell patients there is no one-size-fits-all approach for health," Dr. Tiffany Lowe-Payne, an osteopathic family physician, said. Factors like the patient's genetics and personal history should be considered, along with the diet programs they've tried before and, most importantly, their ability to stick to them."
Lowe-Payne acknowledged that carbohydrates are a mainstay of most people's diets and that, after six months, weight loss is virtually the same as for people on a low-fat diet.
However, she noted that low-carb diets deliver early benefits for patients trying to lower their blood sugar levels or manage insulin resistance.
"When you think of what dieters want — and what they need to stay motivated — it is the satisfaction of results. They want to see significant weight loss and fast. For many, a low-carb lifestyle provides the answer they are looking for," Lowe-Payne explained.